scholarly journals Importance of Zika Virus NS5 Protein for Viral Replication

Pathogens ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 169 ◽  
Author(s):  
Hesham Elshahawi ◽  
Sharifah Syed Hassan ◽  
Vinod Balasubramaniam
Keyword(s):  
Viral Replication ◽  
Zika Virus ◽  
Drug Repurposing ◽  
French Polynesia ◽  
Innate Immune ◽  
Structural Studies ◽  
Rna Dependent Rna Polymerase ◽  
Biochemical Studies ◽  
Major Outbreak ◽  
Virus Survival

Zika virus is the latest addition to an ever-growing list of arboviruses that are causing outbreaks with serious consequences. A few mild cases were recorded between 1960 and 1980 until the first major outbreak in 2007 on Yap Island. This was followed by more severe outbreaks in French Polynesia (2013) and Brazil (2015), which significantly increased both Guillain-Barre syndrome and microcephaly cases. No current vaccines or treatments are available, however, recent studies have taken interest in the NS5 protein which encodes both the viral methyltransferase and RNA-dependent RNA polymerase. This makes it important for viral replication alongside other important functions such as inhibiting the innate immune system thus ensuring virus survival and replication. Structural studies can help design inhibitors, while biochemical studies can help understand the various mechanisms utilized by NS5 thus counteracting them might inhibit or abolish the viral infection. Drug repurposing targeting the NS5 protein has also proven to be an effective tool since hundreds of thousands of compounds can be screened therefore saving time and resources, moreover information on these compounds might already be available especially if they are used to treat other ailments.

scholarly journals Importance of NS5 Protein for Zika Virus Survival

2019 ◽  
Author(s):  
Hesham Elshahawi ◽  
Sharifah Syed Hassan ◽  
Vinod Balasubramaniam
Keyword(s):  
Drug Repurposing ◽  
Fold Increase ◽  
French Polynesia ◽  
Innate Immune ◽  
Mosquito Vector ◽  
Structural Studies ◽  
Aedes Mosquito ◽  
Biochemical Studies ◽  
Major Outbreak ◽  
Virus Survival

ZIKV is the latest addition to an ever-growing list of arboviruses that are causing outbreaks with serious consequences. 14 mild cases were recorded between 1960 and 1980 until the first major outbreak was recorded in 2007 on Yap island followed by more severe outbreaks in French Polynesia (2013) and Brazil (2015) leading to a 20-fold increase in GBS and Microcephaly cases respectively. Various transmission methods have been recorded ranging from Aedes mosquito vector transmission to sexual and vertical transmission. No current vaccines or treatments are available but recent studies have taken interest in the NS5 protein which has both the RdRp & MTase domains making it important for viral replication alongside other important functions such as inhibiting the innate immune system thus ensuring virus survival and replication. Structural studies can help design inhibitors while biochemical studies can help understand the various mechanisms utilized by NS5 thus counteracting them can inhibit or abolish the viral infection. Drug repurposing has proven to be an effective tool since hundreds of thousands of compounds can be screened in-silico thus saving time and resources while also having information available on such compounds especially if they are already used to treat other ailments.

scholarly journals Importance of NS5 Protein to Zika Virus Survival

2019 ◽  
Author(s):  
Hesham Elshahawi ◽  
Sharifah Syed Hassan ◽  
Vinod Balasubramaniam
Keyword(s):  
Drug Repurposing ◽  
Fold Increase ◽  
French Polynesia ◽  
Innate Immune ◽  
Mosquito Vector ◽  
Structural Studies ◽  
Aedes Mosquito ◽  
Biochemical Studies ◽  
Major Outbreak ◽  
Virus Survival

ZIKV is the latest addition to an ever-growing list of arboviruses that are causing outbreaks with serious consequences. 14 mild cases were recorded between 1960 and 1980 until the first major outbreak was recorded in 2007 on Yap island followed by more severe outbreaks in French Polynesia (2013) and Brazil (2015) leading to a 20-fold increase in GBS and Microcephaly cases respectively. Various transmission methods have been recorded ranging from Aedes mosquito vector transmission to sexual and vertical transmission. No current vaccines or treatments are available but recent studies have taken interest in the NS5 protein which has both the RdRp & MTase domains making it important for viral replication alongside other important functions such as inhibiting the innate immune system thus ensuring virus survival and replication. Structural studies can help design inhibitors while biochemical studies can help understand the various mechanisms utilized by NS5 thus counteracting them can inhibit or abolish the viral infection. Drug repurposing has proven to be an effective tool since hundreds of thousands of compounds can be screened in-silico thus saving time and resources while also having information available on such compounds especially if they are already used to treat other ailments.

scholarly journals Comparative Analysis of African and Asian Lineage-Derived Zika Virus Strains Reveals Differences in Activation of and Sensitivity to Antiviral Innate Immunity

2019 ◽  
Vol 93 (13) ◽  
Author(s):  
Katharina Esser-Nobis ◽  
Lauren D. Aarreberg ◽  
Justin A. Roby ◽  
Marian R. Fairgrieve ◽  
Richard Green ◽  
...  
Keyword(s):  
Pattern Recognition ◽  
Viral Replication ◽  
Zika Virus ◽  
Innate Immune ◽  
High Rate ◽  
Immune Signaling ◽  
Brazilian Strain ◽  
Innate Immune Signaling ◽  
Asian Lineage ◽  
Virus Strains

ABSTRACT In recent years, Asian lineage Zika virus (ZIKV) strains emerged to cause pandemic outbreaks associated with a high rate of congenital ZIKV syndrome (CZVS). The reasons for the enhanced spread and severe disease caused by newly emerging strains are not fully understood. Here we compared viral sequences, viral replication, and innate immune signaling induction of three different ZIKV strains derived from African and Asian lineages and West Nile virus, another flavivirus. We found pronounced differences in activation of innate immune signaling and inhibition of viral replication across ZIKV strains. The newly emerged Asian ZIKV strain Brazil Fortaleza 2015, which is associated with a higher rate of neurodevelopmental disorders like microcephaly, induced much weaker and delayed innate immune signaling in infected cells. However, superinfection studies to assess control of innate immune signaling induced by Sendai virus argue against an active block of IRF3 activation by the Brazilian strain of ZIKV and rather suggest an evasion of detection by host cell pattern recognition receptors. Compared to the Asian strain FSS13025 isolated in Cambodia, both ZIKV Uganda MR766 and ZIKV Brazil Fortaleza appear less sensitive to the interferon-induced antiviral response. ZIKV infection studies of cells lacking the different RIG-I-like receptors identified RIG-I as the major cytosolic pattern recognition receptor for detection of ZIKV. IMPORTANCE Zika Virus (ZIKV), discovered in 1947, is divided into African and Asian lineages. Pandemic outbreaks caused by currently emerging Asian lineage strains are accompanied by high rates of neurological disorders and exemplify the global health burden associated with this virus. Here we compared virological and innate immunological aspects of two ZIKV strains from the Asian lineage, an emerging Brazilian strain and a less-pathogenic Cambodian strain, and the prototypic African lineage ZIKV strain from Uganda. Compared to the replication of other ZIKV strains, the replication of ZIKV Brazil was less sensitive to the antiviral actions of interferon (IFN), while infection with this strain induced weaker and delayed innate immune responses in vitro. Our data suggest that ZIKV Brazil directs a passive strategy of innate immune evasion that is reminiscent of a stealth virus. Such strain-specific properties likely contribute to differential pathogenesis and should be taken into consideration when choosing virus strains for future molecular studies.

scholarly journals Zika Virus-Induction of the Suppressor of Cytokine Signaling 1/3 Contributes to the Modulation of Viral Replication

Pathogens ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 163 ◽  
Author(s):  
Rak-Kyun Seong ◽  
Jae Kyung Lee ◽  
Ok Sarah Shin
Keyword(s):  
Immune Responses ◽  
Viral Replication ◽  
Zika Virus ◽  
Viral Gene Expression ◽  
Innate Immune ◽  
Cytokine Signaling ◽  
Viral Gene ◽  
Type I ◽  
Innate Immune Responses ◽  
Suppressor Of Cytokine Signaling

Zika virus (ZIKV) is a mosquito-borne flavivirus that has emerged and caused global outbreaks since 2007. Although ZIKV proteins have been shown to suppress early anti-viral innate immune responses, little is known about the exact mechanisms. This study demonstrates that infection with either the African or Asian lineage of ZIKV leads to a modulated expression of suppressor of cytokine signaling (SOCS) genes encoding SOCS1 and SOCS3 in the following cell models: A549 human lung adenocarcinoma cells; JAr human choriocarcinoma cells; human neural progenitor cells. Studies of viral gene expression in response to SOCS1 or SOCS3 demonstrated that the knockdown of these SOCS proteins inhibited viral NS5 or ZIKV RNA expression, whereas overexpression resulted in an increased expression. Moreover, the overexpression of SOCS1 or SOCS3 inhibited the retinoic acid-inducible gene-I-like receptor-mediated activation of both type I and III interferon pathways. These results imply that SOCS upregulation following ZIKV infection modulates viral replication, possibly via the regulation of anti-viral innate immune responses.

scholarly journals Zika Virus Methyltransferase: Structure and Functions for Drug Design Perspectives

2016 ◽  
Vol 91 (5) ◽  
Author(s):  
Bruno Coutard ◽  
Karine Barral ◽  
Julie Lichière ◽  
Barbara Selisko ◽  
Baptiste Martin ◽  
...  
Keyword(s):  
Drug Design ◽  
Dengue Virus ◽  
Viral Replication ◽  
Binding Site ◽  
Zika Virus ◽  
Neurological Disorders ◽  
Innate Immune ◽  
Viral Mrna ◽  
Structure Based Drug Design ◽  
Content Type

ABSTRACT The Flavivirus Zika virus (ZIKV) is the causal agent of neurological disorders like microcephaly in newborns or Guillain-Barre syndrome. Its NS5 protein embeds a methyltransferase (MTase) domain involved in the formation of the viral mRNA cap. We investigated the structural and functional properties of the ZIKV MTase. We show that the ZIKV MTase can methylate RNA cap structures at the N-7 position of the cap, and at the 2′-O position on the ribose of the first nucleotide, yielding a cap-1 structure. In addition, the ZIKV MTase methylates the ribose 2′-O position of internal adenosines of RNA substrates. The crystal structure of the ZIKV MTase determined at a 2.01-Å resolution reveals a crystallographic homodimer. One chain is bound to the methyl donor (S-adenosyl-l-methionine [SAM]) and shows a high structural similarity to the dengue virus (DENV) MTase. The second chain lacks SAM and displays conformational changes in the αX α-helix contributing to the SAM and RNA binding. These conformational modifications reveal a possible molecular mechanism of the enzymatic turnover involving a conserved Ser/Arg motif. In the second chain, the SAM binding site accommodates a sulfate close to a glycerol that could serve as a basis for structure-based drug design. In addition, compounds known to inhibit the DENV MTase show similar inhibition potency on the ZIKV MTase. Altogether these results contribute to a better understanding of the ZIKV MTase, a central player in viral replication and host innate immune response, and lay the basis for the development of potential antiviral drugs. IMPORTANCE The Zika virus (ZIKV) is associated with microcephaly in newborns, and other neurological disorders such as Guillain-Barre syndrome. It is urgent to develop antiviral strategies inhibiting the viral replication. The ZIKV NS5 embeds a methyltransferase involved in the viral mRNA capping process, which is essential for viral replication and control of virus detection by innate immune mechanisms. We demonstrate that the ZIKV methyltransferase methylates the mRNA cap and adenosines located in RNA sequences. The structure of ZIKV methyltransferase shows high structural similarities to the dengue virus methyltransferase, but conformational specificities highlight the role of a conserved Ser/Arg motif, which participates in RNA and SAM recognition during the reaction turnover. In addition, the SAM binding site accommodates a sulfate and a glycerol, offering structural information to initiate structure-based drug design. Altogether, these results contribute to a better understanding of the Flavivirus methyltransferases, which are central players in the virus replication.

scholarly journals Hepatitis C Virus Infection Is Inhibited by a Noncanonical Antiviral Signaling Pathway Targeted by NS3-NS4A

2019 ◽  
Vol 93 (23) ◽  
Author(s):  
Christine Vazquez ◽  
Chin Yee Tan ◽  
Stacy M. Horner
Keyword(s):  
Hepatitis C ◽  
Viral Replication ◽  
Signaling Pathway ◽  
Transmembrane Domain ◽  
Innate Immune ◽  
Hcv Infection ◽  
Interferon Induction ◽  
Innate Immune Signaling ◽  
Huh7 Cells ◽  
Irf3 Activation

ABSTRACT The hepatitis C virus (HCV) NS3-NS4A protease complex is required for viral replication and is the major viral innate immune evasion factor. NS3-NS4A evades antiviral innate immunity by inactivating several proteins, including MAVS, the signaling adaptor for RIG-I and MDA5, and Riplet, an E3 ubiquitin ligase that activates RIG-I. Here, we identified a Tyr-16-Phe (Y16F) change in the NS4A transmembrane domain that prevents NS3-NS4A targeting of Riplet but not MAVS. This Y16F substitution reduces HCV replication in Huh7 cells, but not in Huh-7.5 cells, known to lack RIG-I signaling. Surprisingly, deletion of RIG-I in Huh7 cells did not restore Y16F viral replication. Rather, we found that Huh-7.5 cells lack Riplet expression and that the addition of Riplet to these cells reduced HCV Y16F replication, whereas the addition of Riplet lacking the RING domain restored HCV Y16F replication. In addition, TBK1 inhibition or IRF3 deletion in Huh7 cells was sufficient to restore HCV Y16F replication, and the Y16F protease lacked the ability to prevent IRF3 activation or interferon induction. Taken together, these data reveal that the NS4A Y16 residue regulates a noncanonical Riplet-TBK1-IRF3-dependent, but RIG-I-MAVS-independent, signaling pathway that limits HCV infection. IMPORTANCE The HCV NS3-NS4A protease complex facilitates viral replication by cleaving and inactivating the antiviral innate immune signaling proteins MAVS and Riplet, which are essential for RIG-I activation. NS3-NS4A therefore prevents IRF3 activation and interferon induction during HCV infection. Here, we uncover an amino acid residue within the NS4A transmembrane domain that is essential for inactivation of Riplet but does not affect MAVS cleavage by NS3-NS4A. Our study reveals that Riplet is involved in a RIG-I- and MAVS-independent signaling pathway that activates IRF3 and that this pathway is normally inactivated by NS3-NS4A during HCV infection. Our study selectively uncouples these distinct regulatory mechanisms within NS3-NS4A and defines a new role for Riplet in the antiviral response to HCV. Since Riplet is known to be inhibited by other RNA viruses, such as such influenza A virus, this innate immune signaling pathway may also be important in controlling other RNA virus infections.

scholarly journals Analysis of Ribonucleotide 5′-Triphosphate Analogs as Potential Inhibitors of Zika Virus RNA-Dependent RNA Polymerase by Using Nonradioactive Polymerase Assays

2016 ◽  
Vol 61 (3) ◽  
Author(s):  
Gaofei Lu ◽  
Gregory R. Bluemling ◽  
Paul Collop ◽  
Michael Hager ◽  
Damien Kuiper ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Zika Virus ◽  
Nonstructural Protein ◽  
Rna Dependent Rna Polymerase ◽  
Antiviral Compounds ◽  
Double Stranded Dna ◽  
Virus Rna ◽  
Potential Inhibitors

ABSTRACT Zika virus (ZIKV) is an emerging human pathogen that is spreading rapidly through the Americas and has been linked to the development of microcephaly and to a dramatically increased number of Guillain-Barré syndrome cases. Currently, no vaccine or therapeutic options for the prevention or treatment of ZIKV infections exist. In the study described in this report, we expressed, purified, and characterized full-length nonstructural protein 5 (NS5) and the NS5 polymerase domain (NS5pol) of ZIKV RNA-dependent RNA polymerase. Using purified NS5, we developed an in vitro nonradioactive primer extension assay employing a fluorescently labeled primer-template pair. Both purified NS5 and NS5pol can carry out in vitro RNA-dependent RNA synthesis in this assay. Our results show that Mn2+ is required for enzymatic activity, while Mg2+ is not. We found that ZIKV NS5 can utilize single-stranded DNA but not double-stranded DNA as a template or a primer to synthesize RNA. The assay was used to compare the efficiency of incorporation of analog 5′-triphosphates by the ZIKV polymerase and to calculate their discrimination versus that of natural ribonucleotide triphosphates (rNTPs). The 50% inhibitory concentrations for analog rNTPs were determined in an alternative nonradioactive coupled-enzyme assay. We determined that, in general, 2′-C-methyl- and 2′-C-ethynyl-substituted analog 5′-triphosphates were efficiently incorporated by the ZIKV polymerase and were also efficient chain terminators. Derivatives of these molecules may serve as potential antiviral compounds to be developed to combat ZIKV infection. This report provides the first characterization of ZIKV polymerase and demonstrates the utility of in vitro polymerase assays in the identification of potential ZIKV inhibitors.

scholarly journals Transmission dynamics of Zika virus in island populations: a modelling analysis of the 2013-14 French Polynesia outbreak

2016 ◽  
Author(s):  
Adam J. Kucharski ◽  
Sebastian Funk ◽  
Rosalind M. Eggo ◽  
Henri-Pierre Mallet ◽  
W. John Edmunds ◽  
...  
Keyword(s):  
South America ◽  
Dengue Virus ◽  
Zika Virus ◽  
French Polynesia ◽  
Neurological Complications ◽  
Transmission Dynamics ◽  
Guillain Barre Syndrome ◽  
Island Populations ◽  
The Pacific ◽  
Guillain Barré

AbstractBetween October 2013 and April 2014, more than 30,000 cases of Zika virus (ZIKV) disease were estimated to have attended healthcare facilities in French Polynesia. ZIKV has also been reported in Africa and Asia, and in 2015 the virus spread to South America and the Caribbean. Infection with ZIKV has been associated with neurological complications including Guillain-Barré Syndrome (GBS) and microcephaly, which led the World Health Organization to declare a Public Health Emergency of International Concern in February 2015. To better understand the transmission dynamics of ZIKV, we used a mathematical model to examine the 2013–14 outbreak on the six major archipelagos of French Polynesia. Our median estimates for the basic reproduction number ranged from 2.6–4.8, with an estimated 11.5% (95% CI: 7.32–17.9%) of total infections reported. As a result, we estimated that 94% (95% CI: 91–97%) of the total population of the six archipelagos were infected during the outbreak. Based on the demography of French Polynesia, our results imply that if ZIKV infection provides complete protection against future infection, it would take 12–20 years before there are a sufficient number of susceptible individuals for ZIKV to reemerge, which is on the same timescale as the circulation of dengue virus serotypes in the region. Our analysis suggests that ZIKV may exhibit similar dynamics to dengue virus in island populations, with transmission characterized by large, sporadic outbreaks with a high proportion of asymptomatic or unreported cases.Author SummarySince the first reported major outbreak of Zika virus disease in Micronesia in 2007, the virus has caused outbreaks throughout the Pacific and South America. Transmitted by the Aedes species of mosquitoes, the virus has been linked to possible neurological complications including Guillain-Barre Syndrome and microcephaly. To improve our understanding of the transmission dynamics of Zika virus in island populations, we analysed the 2013–14 outbreak on the six major archipelagos of French Polynesia. We found evidence that Zika virus infected the majority of population, but only around 12% of total infections on the archipelagos were reported as cases. If infection with Zika virus generates lifelong immunity, we estimate that it would take at least 15–20 years before there are enough susceptible people for the virus to reemerge. Our results suggest that Zika virus could exhibit similar dynamics to dengue virus in the Pacific, producing large but sporadic outbreaks in small island populations.

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